Question

我将数据从json解析为相应的类数据，他们想将它保存在ORMLite中...这里我的类

public class Categories {
    ArrayList<Category> categories;

     public Categories() {
        categories = new ArrayList<Category>();
     }

      public ArrayList<Category> getCategories() { 
          return this.categories; 
     }
}

和级别：

@DatabaseTable(tableName = "levels")
public class Level {
    @SerializedName("id")
    @DatabaseField(id = true)
    int id;

    @SerializedName("title")
    @DatabaseField(dataType = DataType.STRING)
    String title;

    public Level() { }

    public Level(int id, String title) {
         this.id = id;
         this.title = title;
     }
}

DatabaseHandler类中的OnCreate方法：

@Override
public void onCreate(SQLiteDatabase db, ConnectionSource connectionSource) {
     try {  
        TableUtils.createTable(connectionSource, Category.class);
        TableUtils.createTable(connectionSource, Level.class);
     } catch (SQLException e){
         Log.e(TAG, "error creating DB " + DATABASE_NAME);
         throw new RuntimeException(e);
     }
}

DatabaseHandler中的DAO方法：

 public Dao<Category, Integer> getCategoryDao() throws SQLException {
    if (simpleCategoryDao == null) {
        simpleCategoryDao = getDao(Category.class);
    }
    return simpleCategoryDao;
}

  public Dao<Level, Integer> getLevelDao() throws SQLException {
        if (simpleLevelDao == null) {
            simpleLevelDao = getDao(Level.class);
        }
        return simpleLevelDao;
    }

    public RuntimeExceptionDao<Category, Integer> getSimpleCategoryDao() {
        if (categoryRuntimeDao == null) {
            categoryRuntimeDao = getRuntimeExceptionDao(Category.class);
        }
        return categoryRuntimeDao;
    }

    public RuntimeExceptionDao<Level, Integer> getSimpleLevelDao() {
        if (levelRuntimeDao == null) {
            levelRuntimeDao = getRuntimeExceptionDao(Level.class);
        }
        return levelRuntimeDao;
    }

我在我的Activity中以这样的方式解析JSON中的数据：

 DatabaseHandler db = new DatabaseHandler(getApplicationContext());
    JSONObject data = json.getJSONObject(KEY_DATA);
    // getting categories
   JSONArray categories = new JSONArray();
   categories = data.getJSONArray(KEY_CATEGORIES);
     Gson gson = new Gson();
        JsonParser parser = new JsonParser();
        JsonArray array = parser.parse(categories.toString()).getAsJsonArray();
       Type listType = new TypeToken<List<Category>>() {}.getType();
       List<Category> tasks = new ArrayList<Category>();
        tasks = gson.fromJson(array.toString(), listType);
         RuntimeExceptionDao<Category, Integer> simpleDao = getHelper1().getSimpleCategoryDao();
        Dao<Category, Integer> categoryDao = databaseHandler.getCategoryDao();
         Log.i("categoryDAO",categoryDao.queryForAll().toString());

    // getting levels
    JSONArray jsonlevels =new JSONArray();
    jsonlevels = data.getJSONArray(KEY_LEVELS); 
    JsonArray levelsarray = parser.parse(jsonlevels.toString()).getAsJsonArray();
    Type listlevels = new TypeToken<List<Level>>() {}.getType();
    List<Level> levels = new ArrayList<Level>();
    levels = gson.fromJson(levelsarray.toString(), listlevels);
    Log.i("levelsgson",levels.toString());
    RuntimeExceptionDao<Level, Integer> levelDao = getHelper1().getSimpleLevelDao();
    Log.i("levelDAO",levelDao.toString());
    Dao<Level, Integer> levelsDao = databaseHandler.getLevelDao();
    Log.i("levelsDAO",levelsDao.queryForId(3).toString());

我成功获得了类别数据，但是当我想为Level DAO实例调用queryForId（）时我有异常。有这样的例外：

 java.sql.SQLException: queryForOne from database failed: SELECT * FROM `levels` WHERE `id` = ?
    at com.j256.ormlite.misc.SqlExceptionUtil.create(SqlExceptionUtil.java:22)
    at com.j256.ormlite.android.AndroidDatabaseConnection.queryForOne(AndroidDatabaseConnection.java:169)

at com.j256.ormlite.stmt.mapped.MappedQueryForId.execute(MappedQueryForId.java:38)
at com.j256.ormlite.stmt.StatementExecutor.queryForId(StatementExecutor.java:84)
at com.j256.ormlite.dao.BaseDaoImpl.queryForId(BaseDaoImpl.java:219)
at com.assignmentexpert.LoginActivity$1.onClick(LoginActivity.java:119)
at android.view.View.performClick(View.java:2485)
at android.view.View$PerformClick.run(View.java:9080)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3687)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
at dalvik.system.NativeStart.main(Native Method)
      Caused by: android.database.sqlite.SQLiteException: no such table: levels: , while compiling: SELECT * FROM `levels` WHERE `id` = ?
at android.database.sqlite.SQLiteCompiledSql.native_compile(Native Method)
at android.database.sqlite.SQLiteCompiledSql.compile(SQLiteCompiledSql.java:92)
at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:65)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:83)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:42)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1356)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1324)
at com.j256.ormlite.android.AndroidDatabaseConnection.queryForOne(AndroidDatabaseConnection.java:155)
... 15 more

所以问题是“等级”表无法创建。不明白为什么我使用与Category表相同的机制..

经过一些分析，我明白问题在于这个方法

public void saveContacts(List<Category> contacts) throws SQLException
    {

        OrmLiteSqliteOpenHelper dbHelper= DatabaseHandler.getInstance(_context);
        Dao<Category, Integer> daoContact=dbHelper.getDao(Category.class);

        QueryBuilder<Category, Integer> queryBuilder = daoContact.queryBuilder();
        Log.i("dao",queryBuilder.selectColumns("title").prepare().toString());


        for (Category contact : contacts) {
            Log.i("dao",contact.toString());
            HelperFactory.GetHelper().getCategoryDao().create(contact);
        }

    }

在create（）行上。它抛出了一组例外：

    FATAL EXCEPTION: main
 java.lang.NullPointerException
    at com.library.DataParsing.saveContacts(DataParsing.java:61)
    at com.library.DataParsing.fillCategories(DataParsing.java:45)
    at com.library.DatabaseHandler.onCreate(DatabaseHandler.java:85)
    at com.j256.ormlite.android.apptools.OrmLiteSqliteOpenHelper.onCreate(OrmLiteSqliteOpenHelper.java:169)
    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:126)
at com.j256.ormlite.android.AndroidConnectionSource.getReadWriteConnection(AndroidConnectionSource.java:63)
    at com.j256.ormlite.android.AndroidConnectionSource.getReadOnlyConnection(AndroidConnectionSource.java:51)
    at com.j256.ormlite.stmt.StatementExecutor.buildIterator(StatementExecutor.java:202)
    at com.j256.ormlite.stmt.StatementExecutor.query(StatementExecutor.java:155)
    at com.j256.ormlite.stmt.StatementExecutor.queryForAll(StatementExecutor.java:113)
    at com.j256.ormlite.dao.BaseDaoImpl.queryForAll(BaseDaoImpl.java:237)
    at com.assignmentexpert.LoginActivity$1.onClick(LoginActivity.java:97)
at android.view.View.performClick(View.java:2485)
    at android.view.View$PerformClick.run(View.java:9080)
    at android.os.Handler.handleCallback(Handler.java:587)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:123)
    at android.app.ActivityThread.main(ActivityThread.java:3687)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
    at dalvik.system.NativeStart.main(Native Method)

请帮助...

Answer 1

因此，当应用程序第一次运行时，会调用onCreate()方法。如果您以后添加levels表（或修改其架构），则需要增加数据库版本以便可以调用onUpgrade()。

您可以在Android examples主页的ORMLite中看到典型的帮助模式。这是source code for the helper。您的助手需要以下内容。

// any time you make changes to your database objects, you may have to increase
// the database version
private static final int DATABASE_VERSION = 2;
...

@Override
public void onUpgrade(SQLiteDatabase db, ConnectionSource connectionSource,
  int oldVersion, int newVersion) {
    try {
        Log.i(DatabaseHelper.class.getName(), "onUpgrade");
        TableUtils.dropTable(connectionSource, SimpleData.class, true);
        // after we drop the old databases, we create the new ones
        onCreate(db, connectionSource);
    } catch (SQLException e) {
        Log.e(DatabaseHelper.class.getName(), "Can't drop databases", e);
        throw new RuntimeException(e);
    }
}

Answer 2

问题解决了将上下文传递给从OrmLiteSqliteOpenHelper扩展的DatabaseHandler。

ORMLite无法创建第二个表

2 个答案: